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So I'm noticing that along with carb problems the 300 is blowing up smoke by the exhaust manifold. It has had a slight ticking noise under load so I figure I'd check the bolts...
Upon visual inspection I notice one of the bolts (The one visible from under the bonnet right through the hole between the intake and exhaust manifolds) seems to be way out on the stud. Ok, I go behind the wheel with a long socket extension and give it a few turns. "Hey exhaust manifold bolts shouldn't turn this easy" Then bam! the whole thing pops out and I have all the coolant that was in the block now on the garage floor.

What the?!?

Someone please tell me I'm an idiot and everything will be ok.

What did I just do?

Sounds to me like the threads in the block have stripped and you'll have to have it re-tapped as well as use a larger bolt or Helicoil it. I hope not, and I've never heard of this happening on a Packard before. I've had bolts break but never strip out of a block.

Not entirely an uncommon encounter. The fastener shouldn't be a bolt, should be a stud with nut and flat washer. Exhaust manifolds expand at a different rate than the engine block due to the higher temperatures they encounter, so there must be some freedom of movement, hence the attachment with studs, washers and nuts and the oversized (elongated in some cases) holes in the manifold for the fastener. And regardless of how you repair the thread, use shellac or suitable sealant on the stud as they do enter into the cooling jacket, and pay attention to the torque specification.

If tap the block out for a larger stud, is there a trick on how to I keep metal fragments out of the water jacket?

This may sound silly to some but one trick I've found is to magnetize the drill bit as well as the tap. It won't get it all but it'll get most of it. And like Dave says, when you put that new stud back in, make sure you put some sort of sealant on it, you'll be glad you did in the future.

I'm guessing this has been this way for a long time.
The nut was barely on the stud, perhaps 2 turns, but rusted in place. And there was no washer. Looks like someone striped it out previously and then went in deeper to try and get good threads. Then they barely had enough to keep the bolt on.

This one is a first for me. Never taken an exaust manifold off before. I'm imagining lots of heat and penn. oil on the nuts..... And I'm kinda scared now as to what condition the other studs are in. What do I need to be aware of? The Packard service manual doesn't reaally cover 60 yr old manifolds......

Dave, I wouldn't be apprehensive about removing the manifolds, even ones that have been on for 70 years usually come off pretty easily. It's far to simple a proceedure to be covered in a shop manual. A couple of days before, spray the retaining nuts as well as the fasteners where the exhaust header joins the exhaust manifold with your favorite snake oil, many of us like "PB Blaster". Then remove the carburetor and associated vacuum lines and the like, drop the exhaust header, remove the manifold nuts (you'll probably want to go in thru the right front wheel well to make this easier), and normally, off they come, as a pair.

Then let us know what you find as to the condition of the remaining studs.

The nuts should be brass. If they aren't you should replace them with brass ones.

There is little danger from metal particles getting into the cooling system. There will be very little getting in there, when you fill up the motor open up the drain petcock and flush it out. If you run pure water they will rust away very quickly. If you run antifreeze which has a rust inhibitor they will just find their way to the bottom of the radiator and sit there.

The only damage that may happen will be to the water pump seal but I find that unlikely.

I agree that the manifolds should be removed. Then drill as
required and install a Heli-coil, putting sealer on the outside threads. INstall a correct stud using sealer on the outside threads. Good to go for another 55 years.

While you have it apart 2 more things to check. Check the rest of the sutds and check the exhaust manifold heat riser which I will bet my bottom dollar is frozen. Free it up with WD-40, but first buy stock in WD 40 , you may need a lot. You may need to use a torch to free it.

While the side of the motor is unobstructed if teh valve covers are leaking, good time to replace the gaskets.

Enjoy working on a well made, easy to service car. To change a fan belt on a 2010 car you need a PhD.

Fred Kanter
Kanter Auto Products
Boonton NJ

I word of advice I can give is not to separate the two manifolds from one another unless absolutely required. If you do, you may find getting the two manifolds block mounting surfaces aligned and squared again is a real pain in the butt, and sometimes requires machining.

Also since the stud in question is through a water jacket, I would worry to much about the metal fragments from the drilling/tapping operation as you can just flush it out.